<!-- 组件：下拉框 -->
<template>
  <div class="selection-component">
    <div class="selection-show" @click="toggleDrop">
      <span>{{selections[nowIndex].label}}</span>
      <div class="arrow"></div>
    </div>
    <div class="selection-list" v-if="isDrop">
      <ul>
        <li v-for="(item, index) in selections" @click="chooseSelection(index)">{{item.label}}</li>
      </ul>
    </div>
  </div>
</template>
<script>
import { eventBus } from '../../eventBus'
export default {
  /* 接收组件传递过来的参数 */
  props: {
    selections: {
      type: Array,
      default: [{
        label: 'test',
        value: 0
      }]
    }
  },
  data () {
    return {
      /* 下拉框显示隐藏 */
      isDrop: false,
      /* 当前选中第一条数据 */
      nowIndex: 0
    }
  },
  mounted () {
    eventBus.$on('reset-component', () => {
      this.isDrop = false
    })
  },
  methods: {
    /* 下拉框显示隐藏 */
    toggleDrop (event) {
      event.stopPropagation()
      eventBus.$emit('reset-component')//一个页面2个下拉框，前一个无法关闭
      this.isDrop = !this.isDrop
    },
    /* 下拉框展开选中元素 */
    chooseSelection (index) {
      this.nowIndex = index
      this.isDrop = false
      /* 向父级发送一个事件 */
      this.$emit('on-change', this.selections[this.nowIndex])
    }
  }
}
</script>
<style scoped>
  .selection-component {
    position: relative;
    display: inline-block;
  }
  .selection-show {
    border: 1px solid #e3e3e3;
    padding: 0 20px 0 10px;
    display: inline-block;
    position: relative;
    cursor: pointer;
    height: 25px;
    line-height: 25px;
    border-radius: 3px;
    background: #fff;
  }
  .selection-show .arrow {
    display: inline-block;
    border-left: 4px solid transparent;
    border-right: 4px solid transparent;
    border-top: 5px solid #e3e3e3;
    width: 0;
    height: 0;
    margin-top: -1px;
    margin-left: 6px;
    margin-right: -14px;
    vertical-align: middle;
  }
  .selection-list {
    display: inline-block;
    position: absolute;
    left: 0;
    top: 25px;
    width: 100%;
    background: #fff;
    border-top: 1px solid #e3e3e3;
    border-bottom: 1px solid #e3e3e3;
    z-index: 5;
  }
  .selection-list li {
    padding: 5px 15px 5px 10px;
    border-left: 1px solid #e3e3e3;
    border-right: 1px solid #e3e3e3;
    cursor: pointer;
    background: #fff;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;

  }
  .selection-list li:hover {
    background: #e3e3e3;
  }
</style>

